net: ipa: define even more IPA register fields

Define the fields for the FLAVOR_0, IDLE_INDICATION_CFG,
QTIME_TIMESTAMP_CFG, TIMERS_XO_CLK_DIV_CFG and TIMERS_PULSE_GRAN_CFG
IPA registers for all supported IPA versions.

Create enumerated types to identify fields for these IPA registers.
Use IPA_REG_FIELDS() to specify the field mask values defined for
these registers, for each supported version of IPA.

Use ipa_reg_bit() and ipa_reg_encode() to build up the values to be
written to these registers.  Use ipa_reg_decode() to extract field
values from the FLAVOR_0 register.

Remove the definition of the no-longer-used *_FMASK symbols.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>